Numerous rollover protection systems may be found in the prior art. Various prior art rollover protection systems teach various ways for folding down, retracting or telescoping a top portion of a roll bar assembly usually in order to clear low hanging obstacles. Typically, the prior art teaches various types of joints that can be manually adjusted to lower the top portion of a roll bar assembly. A problem that arises when using prior art retractable rollover protection systems arises when an operator begins work in an area which includes low hanging obstacles. The potential exists for an operator to merely place the top portion of a roll bar assembly in a lowered position prior to working in such an area. If the same area also includes a sloped surface and the operator fails to return the top portion of the roll bar assembly to the raised position suitable for protecting the operator during a roll over, the operator will be exposed to a roll over hazard. What is needed is a rollover protection system wherein an operator may quickly and temporarily lower the top portion of a roll bar assembly to clear a low hanging obstacle and which automatically returns to a raised position when the operator is no longer acting to cause the top portion to be lowered. With such a rollover protection system, the top portion of the roll bar assembly would lower only as needed to clear low hanging obstacles and would otherwise remain in a raised position suitable for protecting the operator during a roll over.